摻雜Nb5+、Mo6+、W6+離子對鍺酸鑭基固態氧化燃料電池電解質之影響

本研究是利用固態合成法製備磷灰石結構鍺酸鑭基SOFC電解質材料，實驗分為兩階段，第一階段為改變陽離子缺陷使晶格扭曲，使得自由氧變成間隙氧，進而提高導電率。在第二階段是利用摻雜半徑較大的Nb5+、Mo6+、W6+離子來取代La9.5Ge6O25.25中部分Ge4+ 離子，使間隙氧離子有較大空間傳遞來提高導電率。本實驗對LaxGe5.5Nb0.5O26±δ、LaxGe5.5Mo0.5O26±δ及LaxGe5.5W0.5O26±δ (x=8.75~10)及La9.33Ge6-xNbxO26±δ、La9.33Ge6-xMoxO26±δ及La9.5Ge6-xWxO26±δ (x=0~1.1)材料進行XRD、密度、SEM、XPS及導電率量測。研究結果顯示，鍺酸鑭電解質在經改變陽離子缺陷後再改變摻雜含量的實驗後，各配比在中低溫之導電率皆因摻雜而有大幅度的提升，顯示利用半徑較大的Nb5+、Mo6+、W6+離子取代Ge4+ 離子能有效提高導電率，其中以La9.5Ge5.7W0.3O26.55於1475℃ 燒結後在工作溫度550℃~800℃下之導電率優於8YSZ電解質，於工作溫度800℃時之導電率為3.20 × 10-2 S/cm。

關鍵字

燃料電池；電解質；鍺酸鑭；導電率

並列摘要

The purpose of this study was to develop apatite-type lanthanum germanate-based solid electrolytes for SOFC (Solid Oxide Fuel Cell). In order to achieve the best conductivity of the electrolyte materials applications, these ceramics were doped with various ions with different ionic radius from that of Ge4+ ion and to substitute part of the ion Ge4+ in La9.5Ge6O25.25. Research were showing that a wide range of cation content and dopant substitutions are possible, due to the flexibility of the apatite structure in accommodating a range of ion sizes. First, we examined compositions of different cation content. The result indicated that the ceramics with cation-defects were La9.33Ge5.5Nb0.5O26.245 (3.05×10-2 Scm-1), La9.5Ge5.5Mo0.5O26.75 (3.34×10-2 Scm-1)and La9.5Ge5.5W0.5O26.75 (2.95×10-2 Scm-1), which had the best electrical conductivity of those systems at 800 oC. Second, we studied compositions of different dopant substitutions. The results indicated that the ceramics La9.33Ge5.5Nb0.5O26.245 (3.39×10-2 Scm-1), La9.33Ge5.95Mo0.05O26.045 (3.27×10-2 Scm-1) and La9.5Ge5.7W0.3O26.55 (3.20×10-2 Scm-1) had the best electrical conductivity of these systems, respectively. In addition, the La9.5Ge5.7W0.3O26.55 ceramic sintered at 1475 °C which has better electrical conductivity than 8YSZ at operating temperature of 550°C ~800°C.

並列關鍵字

SOFC ； electrolyte ； lanthanum germanate ； conductivity

參考文獻

2. S.F. Wang, Y.F. Hsu, W.J. Lin, "Effects of Nb5+, Mo6+, and W6+ dopants on the germanate-based apatites as electrolyte for use in solid oxide fuel cells," International Journal of Hydrogen Energy, vol. 38, 2013, pp. 12015-12023.

3. A. Orera, T. Baikie, P. Panchmatia, T.J. White, J. Hanna, M.E. Smith, M.S. Islam, E.Kendrick and P.R. Slater, "Strategies for the Optimisation of the Oxide Ion Conductivities of Apatite-Type Germanates," Full Cells, vol. 1, 2011, pp. 10-16.

4. P.R. Slater, J.E.H. Sansom, J.R. Tolchard, "Development of Apatite-Type Oxide Ion Conductors, " Chemistry Record, vol. 4, 2004, pp. 373-384.

5. J.E.H. Sansom, P.R. Slater, "Oxide ion conductivity in the mixed Si/Ge apatite-type phases La9.33Si6-xGexO26," Solid State Ionics, vol.167, 2004, pp. 23-27.

6. D. Marrero-Lopez, P. Diaz-C arrasco, J. Pena-Martinez, J.C. Ruiz-Morales and J.R. Ramos-Barrado, "Lanthanum Germanate-Based Apatites as Electrolyte for SOFCs," Full Cells, vol. 11, 2011, pp. 65-74.

國際替代計量

摻雜Nb5+、Mo6+、W6+離子對鍺酸鑭基固態氧化燃料電池電解質之影響

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